Complexo crosta negra em seringueira: influência da temperatura e período de molhamento no desenvolvimento da doença em folíolos de seringueira.
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Data
2023-01-20
Autores
Anjos, Louyne Varini Santos dos
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Universidade Estadual Paulista (Unesp)
Resumo
A crosta negra, causada por Rosenscheldiella heveae, tornou-se uma preocupação na produção da seringueira, pois avança rapidamente nas áreas de cultivo no Brasil, causando queda precoce das folhas e consequentemente reduzindo a produção de látex. Este trabalho teve como objetivo avaliar o desenvolvimento de R. heveae, em sua forma sexuada e assexuada (Cladosporium) em folíolos de seringueira do clone comercial RRIM600, sob influência de diferentes temperaturas e períodos de molhamento. Os experimentos realizados com esporos sexuais e assexuados foram montados separadamente. Em ambos os experimentos, os folíolos de seringueira foram previamente desinfestados superficialmente e inoculados com alíquotas contendo 30 μL de suspensão de esporos (105 conídios. mL-1). Após a inoculação dos esporos, os folíolos foram mantidos em câmara úmida a 10, 15, 20, 25, 30, 35 e 40±1 °C no escuro com período de molhamento de 4, 6, 12, 24, 48 e 72 horas. Os estudos foram avaliados por meio do microscópio eletrônico de varredura (MEV) para observação do desenvolvimento do fungo fora da folha e também verificou-se a colonização e reprodução do fungo na parte interna da folha por meio do microscópio eletrônico de luz. As imagens obtidas em MEV, observou-se que os esporos assexuados, Cladosporium, tem seu desenvolvimento rápido, pois 4 horas após a inoculação do fungo é possível verificar a germinação e penetração dos conídios nas temperaturas de 10 a 20 oC. Verificou-se nesta fase, nas temperaturas de 10 a 25 oC, a formação de fiálides, a partir de seis horas após a inoculação, indicando que o fungo já está em período reprodutivo. Na fase sexuada, R. heveae, em MEV, a partir das 4 horas após a inoculação, foi possível verificar a formação de pequenos protuberâncias, que devem ser o início da formação dos estromas, nas temperaturas entre 10 e 20 oC. Estas pontuações negras, nestas temperaturas, evoluem no decorrer dos períodos avaliados, para manchas negras protuberantes circulares, similares aos sintomas de crosta negra, com aparente formação de esporos sobre elas. Os dados obtidos a partir das analises em microscópio UV corroboram com o que foi observado em MEV, mostrando que o fungo tem bom desenvolvimento nas suas duas fases entre as temperaturas de 20 a 25 oC.
Black scab, caused by Rosenscheldiella heveae, has become a concern in rubber tree production, as it is rapidly advancing in growing areas in Brazil, causing early leaf fall and consequently reducing latex production. This work aimed to evaluate the development of R. heveae, in its sexual and asexual form (Cladosporium) in rubber tree leaflets from the commercial clone RRIM600, under the influence of different temperatures and wetting periods. Experiments performed with sexual and asexual spores were set up separately. In both experiments, the rubber tree leaflets were previously superficially disinfested and inoculated with aliquots containing 30 μL of spore suspension (105 conidia. mL-1). After inoculation of the spores, the leaflets were kept in a humid chamber at 10, 15, 20, 25, 30, 35 e 40±1 °C in the dark with wetting period of 4, 6, 12, 24, 48 e 72 hours. The studies were evaluated using a scanning electron microscope (SEM) for observing fungus development outside the leaf and it was also verified the colonization and reproduction of the fungus in the inner part of the leaf by means of the electronic light microscope. The images obtained in SEM, it was observed that the asexual spores, Cladosporium, has a fast development, because 4 hours after the fungus inoculation it is possible to verify the germination and penetration of the conidia at temperatures from 10 to 20 °C. It was verified in this phase, at temperatures from 10 to 25 °C, the formation of phialides, from six hours after inoculation, indicating that the fungus is already in the reproductive period. In the sexual phase, R. heveae, in SEM, from four hours after inoculation, it was possible to verify the formation of small protuberances, which must be the beginning of the formation of stromas, at temperatures between 10 and 20 °C. These black dots, at these temperatures, evolve over the periods evaluated, to circular protuberant black spots, similar to the symptoms of black crust, with apparent formation of spores on them. The data obtained from the UV microscope analyzes corroborate with what was observed in SEM, showing that the fungus has good development in its two phases between temperatures of 20 to 25 °C.
Black scab, caused by Rosenscheldiella heveae, has become a concern in rubber tree production, as it is rapidly advancing in growing areas in Brazil, causing early leaf fall and consequently reducing latex production. This work aimed to evaluate the development of R. heveae, in its sexual and asexual form (Cladosporium) in rubber tree leaflets from the commercial clone RRIM600, under the influence of different temperatures and wetting periods. Experiments performed with sexual and asexual spores were set up separately. In both experiments, the rubber tree leaflets were previously superficially disinfested and inoculated with aliquots containing 30 μL of spore suspension (105 conidia. mL-1). After inoculation of the spores, the leaflets were kept in a humid chamber at 10, 15, 20, 25, 30, 35 e 40±1 °C in the dark with wetting period of 4, 6, 12, 24, 48 e 72 hours. The studies were evaluated using a scanning electron microscope (SEM) for observing fungus development outside the leaf and it was also verified the colonization and reproduction of the fungus in the inner part of the leaf by means of the electronic light microscope. The images obtained in SEM, it was observed that the asexual spores, Cladosporium, has a fast development, because 4 hours after the fungus inoculation it is possible to verify the germination and penetration of the conidia at temperatures from 10 to 20 °C. It was verified in this phase, at temperatures from 10 to 25 °C, the formation of phialides, from six hours after inoculation, indicating that the fungus is already in the reproductive period. In the sexual phase, R. heveae, in SEM, from four hours after inoculation, it was possible to verify the formation of small protuberances, which must be the beginning of the formation of stromas, at temperatures between 10 and 20 °C. These black dots, at these temperatures, evolve over the periods evaluated, to circular protuberant black spots, similar to the symptoms of black crust, with apparent formation of spores on them. The data obtained from the UV microscope analyzes corroborate with what was observed in SEM, showing that the fungus has good development in its two phases between temperatures of 20 to 25 °C.
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Hevea brasiliensis, Temperatura, Molhamento, Rosenscheldiella heveae, Cladosporium Cladosporioides, Temperature, Wetness